From my conversations with the ferry companies in planning a coming trip, it would be wise to book and pay for your trip in advance. Being a Saturday, one of the busier arrival days, always a possibility of the ferry being booked when you get there.

There are only three ferries a day from CA to RT, and RTFF only services Road Town right now. With your 2:30 pm arrival, the 5:00pm ferry is the only one you can catch. Easy to reserve through the RTFF website. Much less expensive than water taxi (50% in most cases).

The other ferry company, Smith's Ferry runs the 2:30pm ferry, in case you could get in earier. But you would need to arrive around 1:00pm to catch that.